The question came in a Dec. 13, 2012, letter, obtained by CNN and first reported by the New York Times, from Rep. Darrell Issa, then-chairman of the House Committee on Oversight and Government Reform, to an array of Cabinet secretaries. It was part of an investigation into the email policies and procedures imposed by the Obama administration on its officials.

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"Have you or any senior agency official ever used a personal email account to conduct official business?" Issa wrote in the form letter. "If so, please identify the account used."

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The letter also asked if the officials used text messages or an alias e-mail account to conduct official business, and requested that the officials outline any policies for record retention across email and social networking sites.

Issa received no response from Clinton directly, and the State Department's only response was to send an outline of the department's email policies in March of 2013 — almost two months after Clinton left the department.

Clinton spokesman Nick Merrill dismissed the story Wednesday in a statement saying "There is nothing new here."

"This was a letter sent to all cabinet agencies leaked to the press two years later at the start of Hillary Clinton's campaign," Merrill said. "The letter was sent shortly before she left the State Department and was responded to in due course. As we've said before, as Secretary, she followed the letter and the spirit of the law. She has provided all of her work email to the State Department and has asked the State Department to release them publicly as soon as possible."